Signs of human activity date back to the Neolithic period, and constant habitation to the 6th century AD. Warwick was a Saxon burh in the 9th century, and Warwick Castle was established in 1068 during the Norman conquest of England. Warwick School claims to be the country's oldest boys' school. The earldom of Warwick, created in 1088, controlled the town in the Middle Ages and built town walls, of which Eastgate and Westgate survive. The castle grew into a stone fortress, then a country house. The Great Fire of Warwick in 1694 destroyed much of the medieval town. Warwick missed industrialisation in the 19th century, but has grown since 1801, when the population was 5,592.

Human activity on the site of the town dates back to the Neolithic, when a settlement may have been established. Archaeological work on the site of Warwick School in 2017–18 has revealed the footings of a sizeable Roman barn, dating from the second century AD. From the 6th century onwards, Warwick has been continuously inhabited. According to the Anglo-Saxon Chronicle, in the year 914 the Anglo-SaxonEthelfleda Lady of the Mercians, daughter of king Alfred the Great and sister of king Edward the Elder of Wessex, built a burh or fortified dwelling at Warwick. It was one of ten burhs built to defend the kingdom of Mercia against the Danes. Warwick was chosen as the site for one of these fortifications because of its proximity to the important transport routes of the Fosse Way and the Avon. In the early 10th century a new shire was founded with Warwick as its administrative centre, giving the settlement new importance. The name Warwick means "dwellings by the weir". In 1050 the Danes invaded Mercia and burned down much of Warwick including the nunnery (which stood on the site of the present day St Nicholas Church).

William the Conqueror founded Warwick Castle in 1068 on his way to Yorkshire to deal with rebellion in the north. Building a castle within a pre-existing settlement could require demolishing properties on the site, and in the case of Warwick four houses were pulled down. The castle was within the larger Anglo-Saxon burh and a new town wall was created close to the rampart of the burh.

In the medieval period Warwick remained under the control of various Earls of Warwick, mostly of the Beauchamp family, becoming a walled town. Today the only remains of the town walls are the east and west gatehouses. The eastern gatehouse is now a holiday home, but formerly served as part of the King's High School, a sister institution to Warwick School. Warwick was not incorporated as a borough until 1545. The town's Priory was founded in 1142 on the site of the current Priory Park.